A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a vehicle is equipped with a navigation function to guide a driver to a destination through a calculated route. Such a navigation system detects the position of the user's vehicle, and reads out map data pertaining to an area at the current vehicle position from a data storage medium, for example, a CD-ROM (compact disc read-only memory), a DVD (digital versatile disc), or a hard disc. Typically, the navigation system displays a map image on a monitor screen while superimposing thereon a mark representing the current location of the user.
When a destination is specified by a user, the navigation system determines a route to the destination based on, for example, the shortest way to reach the destination, the route using many free ways as possible or the route without using toll road, and the like. After determining the calculated route, the navigation system starts the route guidance operation to guide the user along the calculated route to the destination. Typically, the navigation system shows the intersection to show the next turn and a direction of the turn where such a turn is necessary at the intersection. Such route guidance by the navigation system is also accompanied by voice instructions.
The navigation system displays a map image on a monitor screen on which various map elements such as streets including the calculated route to the destination, fields, rivers, mountains, buildings, etc., as well as various icons are illustrated. The user is able to scroll the illustrated image on the screen to change the map image to that of the desired location. The map image is used not only to see the map of the area that surrounds the current user (current vehicle) position but also to find a specific location or an address of a particular place such as a favorite restaurant, gas station, etc. and to pin-point such a desired location on the screen of the navigation system.
When searching a particular location on the map image, there are many cases that the user wants to search a particular city first to narrow down the particular location within the city. This is because an address of a particular location, such as a destination that the user wants to visit, is typically defined by a street name, a house number, and a city name, and the navigation system needs such address information to determine a route to the destination. However, when the user wants to find a particular city on the map image, the user may often have a difficulty in specifying a desired city for the navigation system. Especially, it is difficult to find a city when the user is not familiar with the area where he/she wants to find the city because the user is from the other state, etc.
In many cases, the user would have to type-in the name of a city through a keyboard, however, the user may not know the exact spelling of the city name. Further, to maintain the safe driving, the user has to stop the vehicle for typing the city name, which is inconvenient when the user is driving the vehicle. Thus, a method of typing the particular city name for the navigation system is error-prone, inconvenient and dangerous.
If the user knows the abstract location of the desired city, the user may be able to find the city by browsing or scrolling the map image by operating a scrolling key, etc. However, scrolling the map image on the screen while driving a vehicle may be prohibited because it adversely affects the safe driving. Accordingly, there is a need of a new display method and apparatus which is conveniently designed for searching a city or cities on the map image of the screen of the navigation system.